Children will be eligible for this study if they (1) are aged 10 to 18 years, (2) diagnosed with cancer, (3) prescribed CTX, (4) are not receiving concomitant radiation, and (5) have not undergone bone marrow transplantation. Patients with central nervous system tumors will be ineligible because sleep problems have been associated with brain injury. Besides, patients with osteosarcoma and bone metastasis will not be recruited because they may have troubles with walking. Based on the power analysis, a total of 160 eligible patients will be recruited, N = 80 for the control and N = 80 for the intervention group.